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Thread: allergies

  1. #1
    Join Date
    Dec 2012



    I live in a townhome that was built around 1980. All ductwork and insulation is original as far as I know. I have terrible sinus allergies in this place. For years I just dealt with it, blowing my nose often. It is only on a recent trip to an ear nose and throat doctor that I discovered my allergies could do long term damage to my ears.

    A couple years ago I removed all the carpet and replaced it with laminate flooring, but while that helped a little, it did not solve the problem. I then had the ducts cleaned but again this did not help. Last week a consultant from a large hvac company came out to quote me on some work.
    He recommended replacing the ducts in the attic, taking out all the old insulation and replacing it with new insulation. He said since the ducts were so old, it was likely that they had leaks and all the crap in the attic including the insulation was being blown into the house. There is also old insulation wrapped around all the ducts that he said was probably getting into the ducts and blown into the house. I'm no expert but what he said all seems to make sense.

    Now for the downstairs. The dstairs ducts cannot be accessed. He recommended doing an aeroseal job on them to seal them up and then cleaning the ducts ( or cleaning and then aeroseal, I cant remember the order). I do not know what it looks like around the ducts dstairs, but I would guess it is just as nasty as what it looks like in the attic. My concern is that the aeroseal site says it seals up to 80% of leaks. My thinking is that if there is a lot of nasty stuff around the down stairs ducts, it can still get into the ducts through the 20% that remains unsealed after the ducts have been cleaned.

    So all that was recommended was upstairs: replace upstairs ducts, remove old insulation and add new insulation

    dstairs: aeroseal and clean ducts

    The cost is hefty. I will say, the last 2 days I have not been running my central heat at all my allergies have improved quite a bit, so it does seem like I'm allergic to something coming out of the ducts. I will probably turn the central heat back on soon just to confirm that. My question is, does doing this sound like a good plan? Do you think aerosealing and cleaning the down stairs ducts will improve my situation, even if it only seals 80% of the leaks?

    I have already done everything in my power to eliminate dust and mold inside the house. I already clean every day, i've removed all old blinds, curtains are brand new or have just been washed etc. Thanks

  2. #2
    Join Date
    Dec 2012
    Seattle, WA
    You need to make sure the company is using mastic to seal all the ductwork. Many companies either don't do this or use tape. Tape does not create a good seal and will fail over time. Are the ducts in the basement in an unconditioned space like a crawl space? I would make sure that you get a video inspection on any ductwork that cannot be accessed. If you have ductwork that is disconnected in areas that you cannot seal then the Aeroseal won't do you any good. Get proof - pictures / video. You want to deal with someone that is very thorough in their approach. Find out it the attic ductwork was sealed properly as well as the return air. I wouldn't focus on filtration systems until you get an idea of what that downstairs ductwork looks like.

  3. #3
    Join Date
    Dec 2012
    Tks for the reply. There is no basement here.

  4. #4
    Join Date
    Dec 2002
    The first thing an Aeroseal machine does is a Duct Blaster test, you will know exactly what your rate of leakage is to start with and what you end up with. Leakage in single digits at 25 pascals is not uncommon after sealing.
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  5. #5

  6. #6
    Join Date
    May 2004
    south louisiana
    there is no need to remove insulation from the attic.
    what you want to do is to seal the areas in the ceiling where this
    insulation on the attic floor enters the living space.

    what type of insulation is in the attic?
    where are your supply grills located? location of return air grills?
    do you have recessed lights?
    what is attic access..door, hatch, pull down stair?
    bath fans in ceiling & stove vent through ceiling?

    a blower door test will show you house leakage.
    once these areas are sealed...paying special attention to ceiling
    penetrations..then insulation particles will stay out of living space.
    and allergy symptoms lessen.

    replacement of ducts that are acessable is a good idea if they are flex duct.
    if they are hard pipe, you would have to compare costs between unwrapping
    mastic seal and re-wrapping with R-8 ductwrap to replacing with flex.

    for ductwork not acessable, aeroseal is a big cost for a product that only seals
    small leakage sites. any areas over3/4- 5/8" are too big for aeroseal to seal.
    in some cases the ducts seal better if not cleaned. aeroseal encapsulates
    suff in ducts.

    sealing returns air tight is also recommended. use only UL 181 code approved
    mastic and mastic tape. not foil or duct tapes. my prefrence is Hardcast brand
    #1402 mastic tape. strong, seals well and long term seal.

    a good plan of action is to start sealing what you know leaks, and work towards
    larger areas to seal.

    independent (not aeroseal) duct testing should be done prior to any
    work pinpoint leakage sites. and then again after work is completed.

    remove a supply grill to get an idea of how big the leakage site is
    where supply box enters the living space.
    I find this to be an important leakage site because it is surrounded
    by insulation. I seal with mastic tape, because caulk doesn't stick
    to sheetrock dust. also when supply boxes are caulked where the
    penetrate, and the grill is installed..the caulk sticks to the grill
    & not the hole.
    attached is a pic of how I seal these areas. same can be used
    for bath fans by removing cover & sealing housing to ceiling.

    other pics are open wall in return, with ductboard cut to fit
    to seal this area. ductboard would then be mastic sealed in place.

    once you have done all the sealing work...upgrade to a media filter
    attached is media filter that fits into existing return.

    best of luck
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  7. #7
    Join Date
    Dec 2002
    Good post. Just make sure that after all duct sealing is done and high efficiency filter is installed that the TESP of the system is checked for proper air flow against manufacturer's specs. It is VERY common that after duct sealing the system will no longer have proper airflow. If all is good don't forget to adjust your refrigerant charge to proper SH and or SC.
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  8. #8
    Join Date
    Feb 2013
    The way most people I have talked to discover exactly if the problem is in the HVAC system is:

    They turned the unit off and they felt better or symptoms were eliminated.

    In these cases, replacing ductwork was necessary because of bacterial/fungal growth in the supply ductwork.

    Careful inspection of unit, insulation and ductwork is critical.

    One thing I have found each one had in common is: insufficient return duct CFM.

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